This invention relates to a method and an apparatus for supplying a liquid crystal into a cell.
In general, a cell of a liquid crystal display exhibits a rectangular configuration. It has an injection port (first port) and an exhaust port (second port) formed in a first and a second edge portion of opposing short sides thereof, respectively. After the interior of the cell is evacuated to a predetermined degree of vacuum through the exhaust port, a pressurized liquid crystal is injected into the cell through the injection port. However, since a gap between two substrates constituting the cell is very narrow, the injected liquid crystal becomes increasingly large in pressure loss as it moves away from the injection port. For this reason, injection velocity of the liquid crystal coming through the injection port is lowered and therefore, much time is required to fill the cell with the liquid crystal, especially in the case where the cell is large in size.
Japanese Patent Unexamined Publication (Kokai) No. Hei 8-262461 discloses a method in which first, an evacuating operation is performed not only at the exhaust port but also at the injection port and when the interior of the cell reaches a predetermined degree of vacuum, the evacuating operation is switched over to a liquid crystal injecting operation at the injection port while the evacuating operation is continuously performed at the exhaust port. Although it is possible for this method to reduce the time required for evacuating the interior of the cell to a predetermined degree of vacuum, it is impossible for the method to reduce the time from the start of liquid crystal injection to the completion of liquid crystal injection.
In a method for supplying a liquid crystal disclosed in Japanese Patent Unexamined Publication (Kokai) No., Hei 9-5761, intermediate ports (third and fourth ports) are formed respectively in third and fourth edge portions of long sides of the cell orthogonal to the first and second edge portions. After the liquid crystal which has been injected into the cell from the injection port reaches the intermediate ports, a liquid crystal is also injected therein from the intermediate ports. By this, the time required for filling the liquid crystal can be reduced.
In the method disclosed in the second-mentioned Publication, no air is discharged through the intermediate ports. Therefore, the step for increasing the interior of the cell to a predetermined degree of vacuum and the following step for bringing the injected liquid crystal to the intermediate ports are substantially same as in the case where no intermediate ports are employed. Thus, time is not reduced in those steps.